The present invention relates generally to an improved vibration damper for a motor vehicle suspension system. More specifically, the present invention relates to an improved floating rod guide for the vibration damper.
Vibration dampers are used in shock absorbing systems connected to motor vehicles to dissipate vibrational and other forces. Such vibration dampers are used to absorb shock loads sustained by the wheel assemblies of such vehicles and are used in combination with coil springs to dissipate vibration generated from such variables as rough road surfaces, potholes, and unbalanced tires. These dampers typically operate by transmitting the applied forces to a piston slideably mounted in a fluid filled chamber in the damper. As the piston strokes through the chamber, the fluid in the chamber is forced through and around the piston. The resistance of the piston to movement through the fluid in the chamber is proportional to the applied force. Accordingly, these forces are dampened, thereby reducing the amount of vibration transferred to the passenger compartment.
Strut or shock type dampers may include a rod guide assembly that guides and centers the piston shaft and the piston as they stroke within an inner tube. When lateral or xe2x80x9cside loadxe2x80x9d forces are applied to the damper, the piston shaft and the piston may be shifted away from the radial center of the damper. Furthermore, deviations in tolerance in the various components of the damper can also shift the piston shaft and the piston off center. Radial misalignment of the rod and the piston within the damper causes the shaft to rub against the rod guide as it strokes within the inner tube, which increases wear on the piston shaft and the rod guide. This is particularly undesirable in dampers containing magnetorheological fluid because the suspended magnetic particles can be abrasive to the piston shaft. Further, when the shaft is laterally displaced, the shaft can engage and laterally displace the rod guide, which in turn shifts the inner tube from the radial center of the damper. Radially shifting any of the components in the vibration damper increases wear upon the various bearings, seals, and sleeve supports inside the damper effectively reducing the service life.
In order to prevent undue wear to the piston shaft, some vibration dampers are provided with an outer housing bearing, and a bracket adjacent its lower end for attachment to a vehicle wheel suspension assembly. One end of the piston shaft is fixed to the middle of the damper base, and the shaft projects upwardly into the inner tube containing the piston and the fluid. The top of the inner tube is fixed to the vehicle body, so that the shaft and the piston move axially together with the outer housing and a wheel assembly in opposition to the inner tube and the vehicle body. Side loads to the damper are received by bearing elements between the inner tube and the outer housing, and very little of the side loads are thus applied to the shaft. However, a support must be provided to close and seal the bottom of the inner shaft against loss of the working fluid. Further, the support ring must accommodate the stroking action of the shaft therethrough.
The support ring includes a rod guide and seal assembly, which, although relieved of most of its side loads, still includes a bearing and a seal in contact with the shaft. The rod guide and the seal assembly thus provide a third point of radial support for the rod between the point of attachment to the damper base at the bottom and the piston at the top. If manufacturing tolerances or other factors cause the rod guide to be laterally misaligned with these other supports, it may cause undesirable wear between itself and the piston shaft.
It is imperative for the rod guide and seal assembly to accommodate manufacturing tolerances in lateral alignment with other rod support apparatus while providing secure sealing around an axially moving piston shaft to maintain the working fluid within the working chambers of the damper.
To facilitate the lateral alignment and the sealing function around the piston shaft, a complex support ring has been introduced into vibration dampers of this type. These support rings include moveable components that utilize an empty volume within a housing support ring. The empty housing is filled with grease to impede fluid penetration into the support ring. However, iron particles suspended in the fluid, i.e. M.R. Fluid, can collect within the support ring thereby immobilizing the piston shaft and making it nonfunctional. Additionally, during manufacturing of the vibration damper the grease application is a difficult and messy operation which requires additional tooling. Furthermore, redundant seals are required on either side of the piston shaft to prevent fluid leaks into the support ring. These redundant seals increase the sliding friction on the piston shaft causing undue side load and wear in the vibration damper.
Therefore, it would be desirable to introduce a support ring to the vibration damper that is mechanically simple and yet, provides the lateral support required to maintain functionality of the vibration damper.
The present invention comprises a vibration damper having an inner tube concentrically aligned within an outer housing. A piston shaft having a piston attached at an end thereof is inserted into the inner housing. The piston strokes within the inner tube, which is filled with fluid, and thereby reduces the vibrational forces derived from such variables as rough road surfaces, potholes, and unbalanced tires. A support ring encloses the inner tube, thereby defining a pumping chamber within the inner tube. The piston shaft is inserted through the support ring which provides lateral support to the piston shaft. The support ring includes a seal cover, which has an inner surface with a rim. A rod guide is inserted into the sealed cover and abuts the rim. The rod guide includes a central aperture into which the piston shaft is inserted. The rim is sandwiched between the rod guide and a washer onto which the rod guide is affixed. The rod guide floats within the circumference of the rim providing lateral motion to the piston shaft.
The present invention eliminates the manufacturing and performance problem associated with the prior art support rings. By affixing the rod guide to the washer and sandwiching the rim therebetween, the empty volume associated with the prior art can be eliminated. Further, because there is no empty volume inside the support ring, the redundant seals may be eliminated. Still further, the design of the present invention provides a lateral support equal to the complex designs used in the prior art support rings.